Antibiotic residues in foods are a major food safety concern. Health issues include bacterial resistance to drugs and allergic reactions. To avoid the impact of such health issues, food is tested worldwide for antibiotics and other contaminants. One type of test method uses what is commonly known as a lateral flow test strip.
Lateral-flow test strips for detecting one or more analytes in a fluid sample may include a capture agent immobilized within a region of the test sometimes referred to as a detection zone. Detection zones can include test zones and control zones. A typical capture agent has binding affinity for a substance that may be in the mobile phase of the test strip.
Lateral-flow tests in which the binding of a substance from a mobile phase to a capture agent generates a visible signal, that can be interpreted visually or using a reader, such as a spectrophotomer, are well known in the art. Examples of such devices are described in U.S. Pat. No. 5,985,675, issued Nov. 16, 1999; and U.S. Pat. No. 6,319,466, issued Nov. 20, 2001, and U.S. patent application Ser. No. 10/289,089, filed Nov. 6, 2002 (based on U.S. Provisional Application 60/332,877, filed Nov. 6, 2001) all of which are incorporated herein by reference.
Lateral-flow tests are widely used in the food products industry. One application is in testing milk. The United States Food and Drug Administration (FDA) requires that bulk milk tankers be tested for unsafe levels of beta-lactam antibiotics. The sensitivity required pursuant to Appendix N of the Pasteurized Milk Ordinance is: amoxicillin 10 parts per billion (“ppb”), ampicillin 10 ppb, penicillin G 5 ppb, ceftiofur 50 ppb, cephapirin 20 ppb, and cloxacillin 10 ppb (the “safe levels”). The FDA also requires that certain milk tests be automatically (electronically) analyzed and recorded. It is desirable, therefore, to provide milk-testing personnel with a user-friendly test that can be analyzed with or without a reader and can detect multiple beta-lactams, including the six beta-lactams listed above (“the target beta-lactams”), when present at or above the safe level.